1896. | MYOLOGY OF RODENTS. ll 
In Microtus, Rhizomys, Bathyergus, and Hydromys, however, only 
three lumbricals were seen, the radial one having been suppressed. 
Pronator Quadratus—This muscle is less well developed as a 
rule than in the Hystricomorpha, never, so far as I have seen, 
extending along the length of the bones. In Myoxus and Microtus 
it occupies the middle third of the forearm; in Cricetomys, 
Cricetus, and Mus barbarus the lower half. In the Gerbille it 
attains its maximum of development, and is attached to the lower 
three-quarters of the two bones. In Georychus, Bathyergus, 
Rhizomys, and Siphneus it is a very feeble muscle—in the two 
former being found only opposite the insertion of the pronator 
radii teres, while in the two latter it is represented by a few fibres 
between the lower ends of the two bones. 
Supinator Longus.—This muscle was wanting in every animal 
dissected. Windle found it absent in Hydromys, and Milne- 
Edwards says that it is also wanting in Stphneus, Spalax, and 
Helamys. He states, however, that it is present in the Hamster, 
and, although it was most certainly absent in the Hamster I 
dissected, I take his statement to mean that very occasionally a 
supinator longus may be found among the Myomorpha as a 
reversion to the Sciuromorphine type. 
Extensor Carpi Radialis Longior and Brevior.—In all the 
animals examined these muscles had the usual attachments. 
When there is any difference in size, as in the case of Myowus, 
Georychus, Rhizomys, and Siphneus, the brevior is the larger 
muscle. Milne-Edwards says that in Georychus and Spalax there 
is only one radial extensor, but he does not mention where that 
one is inserted. Unless the insertion is carefully looked for the 
two muscles may easily be mistaken for one, as they le very close 
to one another. 
Extensor Communis Digitorwm.—The only point of interest in 
the Myomorphine common extensor is whether it goes to the 
fifth digit or not. In Georychus, Bathyergus, Siphneus, and Mus 
barbarus no slip is given to the little finger. In Cricetomys two 
tendons pass to the middle, and in Rhizomys two to the ring 
finger. 
Extensor Minimi Digitii—The insertion of this muscle was into 
the fourth and fifth fingers in Gerbillus, Microtus, Myodes, Mus 
barbarus, Hydromys, Georychus, Buthyergus, and Rhizomys. In 
Bathyergus, however, the tendon to the fourth digit was very 
small. In Cricetus it was attached to the third and fifth digits, 
while in Myoxus and Cricetomys it only went to the fitth. 
Extensor Carpi Ulnaris.—Nothing special was noticed in the 
attachments of this muscle. Milne-Edwards describes it as a 
double muscle in Siphneus, one tendon going to the base of the 
fourth, and the other to the base of the fifth metacarpal bone, 
at the same time he does not describe any extensor minimi digiti. 
Considering the very constant character of the extensor carpi 
ulnaris in Rodents, and the comparative inconstancy of the 
extensor minimi digiti, I expect that the explanation of what he 
